Projection display

ABSTRACT

A projection type image display apparatus is provided which includes a housing to hold an optical system including multi-lenses, a polarized-light conversion element and a color separation portion. The housing operates to provide an optical path between a light source, located outside the housing, and penetration-type image display elements and an optical synthesizing portion also located outside of the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/419,423, filed Apr. 7, 2009, which, in turn, is a continuation ofU.S. application Ser. No. 11/500,993, filed Aug. 9, 2006 (now U.S. Pat.No. 7,532,407); and which applications claim priority from JapanesePatent Application 2005-231052, filed Aug. 9, 2005, the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a projection-type image displayapparatus, for modulating light intensity of lights irradiated from anillumination optic system, through liquid crystal image display elements(i.e., panels) for use of lights of R, G and B, in particular, applyingpolarization effect therein, thereby forming an optic image, andprojecting said optic image upon a screen through a projection opticsystem.

Conventionally, the projection-type image display apparatus was alreadyknown by a name, such as, a liquid crystal projector or the like, forexample, i.e., containing an optical unit, as well as, an electricsource circuit and/or a video driver circuit within a housing thereof,for projecting the optic image that is formed through modulating thelight intensity upon the lights from a light source, with applyingpolarization effect thereto, so as to vary the density for each ofpixels, depending on an image signal through light valve elements foruse of R-, G- and B-lights, and thereby projecting the said optic imageformed onto the screen or the like, by means of a projection lens.Further, at present, as such the light valve element mentioned above isalso widely known and practically used, for example, so-called atransmission or a transparent-type liquid crystal panel, or areflection-type liquid crystal panel, etc.

As the optic unit of such the projection-type image display apparatus isalso already known an optic unit, as is disclosed in Japanese PatentLaying-Open No. 2004-126496 (2004) or Japanese Patent Laying-Open No.2004-184889 (2004), for example, wherein the optic image is formedthrough cross dichroic prisms, functioning as a color synthesizingelement, after conducting the light-intensity modulation on the lights,which are divided with applying the polarization functions, by means ofthe reflection-type liquid crystal panels for use of the R-, G- andB-lights, and thereby projecting the optical image formed onto thescreen or the like, through the projection lens.

Also, an optical unit is already known, in Japanese Patent Laying-OpenNo. 2005-12303 (2005), for example, (in particular, in the secondembodiment shown in FIGS. 3 and 4) wherein the optic image is formedalso through the cross dichroic prisms, as the color synthesizingelement, but conducting the light intensity modulations of R, G and Blights, with applying the transparent-type liquid crystal panels (or,the transparent-type light valves) therein, in the place of such thereflection-type liquid crystal panels as mentioned above, and therebyprojecting the optic image formed onto the screen or the like, throughthe projection lens.

Also further is already known a cooling structures within the optic unitof projecting the optic image on the screen or the like, which is formedthrough the cross dichroic prisms while conducting the light intensitymodulations of R, G and B lights with applying the reflection-typeliquid crystal panels (or, the reflection-type light valves) or thetransparent-type liquid crystal panels (or, the transparent-type lightvalves) therein.

SUMMARY OF THE INVENTION

By the way, as the light source within the projection-type displaymentioned above, such as, the liquid crystal projector, etc., ingeneral, there is used a high-pressure discharge lamp, such as, a metalhalide lamp and a high-pressure mercury lamp, etc., for example, becauseof the reasons that the conversion efficiency there of is high and thatlights can be easily obtained therewith, being very similar to thatirradiated from a point-like light source. However, with such the liquidcrystal projector, it is tried to obtain high-brightness, as well as,high-definition, accompanying with large-sizing of a display screenthereof, i.e., adopting a high-output lamp therein (for example, themetal halide lamp having an electric power, being equal to 250 W orlarger than that), and for this reason, ill-influences are exerted onthe characteristics of the liquid crystal panels, by the heatsgenerating from such the light radiation source of high output, andfurther the heat-generation of the liquid crystal panels due toirradiation of strong lights from that light radiation source.

Then, conventionally, within such the projector, for the purpose ofpreventing various portions of the apparatus including the liquidcrystal panel (in particular, a lamp and a controller portion thereof)from increasing of temperature, i.e., protecting them from theill-influences thereof, there is provided a fan for use of air cooling,and thereby introducing/circulating cooling air from an outside of theapparatus into an inside of a housing thereof. Further, as is alreadyknown in Japanese Patent Laying-Open No. 2004-354795 (2004), an attemptis made for cooling down the cross dichroic prisms including the liquidcrystal panels, which is installed within the housing while beingmounted on an attachment member having a cooling fin on one-side surfacethereof, thereby to obtain cooling through a cooling air current withinthat housing.

On the other hand, with the reflection-type liquid crystal panels or thetransparent-type liquid crystal panels, to be applied as the lightintensity modulating elements within such the optic unit, also demand ismade remarkably for small-sizing, as well as, for low-costs thereof, inrecent years, and therefore the strong lights emitted from the lightradiation source are irradiated upon the liquid crystal panels, eachhaving a smaller surface area thereof. For this reason, the heatgeneration on the liquid crystal panel due to the light irradiationcomes up to be large much more, but on the contrary to that, it isdifficult by any possibility, to suppress such the heat-generation onthe liquid crystal panel as was mentioned above, fully by only means ofthe introduction and/or the circulation of cooling air into the insideof the apparatus by means of the air-cooling fan mentioned above.

Then, according to the present invention, by taking the drawbacks of theconventional arts mentioned above into the consideration thereof, i.e.,an object thereof is to provide the practical structures of the opticunit, in particular, for enabling to achieve the optical performancesdesired, depending on necessity thereof, dissolving those deteriorationsin performances that are caused due to the heat generation mentionedabove, within the projection-type image display apparatus,representatively, such as, the liquid crystal projector, for example,upon which requirements are made strongly for the high-definition, aswell as the high-brightness thereof, and in other words, an improvedprojection-type image display apparatus.

Namely, according to the present invention, first of all, there isprovided a projection-type image display apparatus, comprising thefollowings in a housing thereof: a light source; an illumination opticsystem; penetration-type image display elements for R-, G- and B-lights;an optical synthesizing means, and a projection lens, wherein theR-light penetration-type image display element, the G-lightpenetration-type image display element and the B-light penetration-typeimage display element are attached on surfaces different from each otherof the said cross dichroic prisms, for building up the opticalsynthesizing means, onto which the display elements are attached, in onebody, so that the said cross dichroic prisms attached with the displayelements thereon can be attached, detachably, while opposing to asurface different from those, on which the display elements areattached, to an incident surface of the projection lens.

Further, according to the present invention, there is also provided aprojection-type image display apparatus, comprising the followings in ahousing thereof: a light source; an illumination optic system;reflection-type image display elements for R-, G- and B-lights; anoptical synthesizing means, and a projection lens, wherein the R-lightpenetration-type image display element, the G-light penetration-typeimage display element and the B-light penetration-type image displayelement are attached with the said cross dichroic prisms for building upthe optical synthesizing means, in one body, on optical paths opposingto surfaces thereof different from each other, so that the said crossdichroic prisms attached with the display elements thereon can beattached, detachably, while opposing to a surface different from those,on which the display elements are attached, to an incident surface ofthe projection lens.

BRIEF DESCRIPTION OF THE DRAWINGS

Those and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription when taken in conjunction with the accompanying drawingswherein:

FIG. 1 is a block diagram for showing the entire structures of aprojection-type image display apparatus, which applies transparent-typeliquid crystal elements (or panels) therein, according to an embodiment1 of the present invention;

FIG. 2 is a partially exploded perspective view for showing the detailedstructures of a cross dichroic prisms, as being an optical synthesizingmeans, and the transparent-type liquid crystal elements for use of R, Gand B color lights, in the projection-type image display apparatusmentioned above;

FIG. 3 is also a partially exploded perspective view for showing thedetailed structures of the cross dichroic prisms, as being the opticalsynthesizing means, and the transparent-type liquid crystal elements foruse of R, G and B color lights, in the projection-type image displayapparatus mentioned above;

FIG. 4 is a partially enlarged perspective view for showing the detailsof the cross dichroic prisms mentioned above;

FIG. 5 is a partially enlarged perspective view for showing thecondition when installing the cross dichroic prisms, on which areattached the transparent-type liquid crystal elements for use of R, Gand B color lights, onto an attachment structure;

FIG. 6 is also a partially enlarged perspective view for showing thecondition when installing the cross dichroic prisms, on which areattached the transparent-type liquid crystal elements for use of R, Gand B color lights, onto the attachment structure;

FIG. 7 is a partially enlarged perspective view for showing thecondition after installing the cross dichroic prisms, on which areattached the transparent-type liquid crystal elements for use of R, Gand B color lights, onto the attachment structure;

FIG. 8 is a perspective view of the projection lens after beinginstalled with the cross dichroic prisms, on which are attached thetransparent-type liquid crystal elements for use of R, G and B colorlights, onto the attachment structure;

FIG. 9 is a block diagram for showing the entire structures of aprojection-type image display apparatus, according to an embodiment 2 ofthe present invention;

FIG. 10 is a block diagram for showing the entire structures of aprojection-type image display apparatus, applying reflection-type imagedisplay elements therein, according to an embodiment 3 of the presentinvention; and

FIG. 11 is a partially enlarged perspective view for showing the detailsof the structures for installing the optical synthesizing means,including the cross dichroic prisms, thereon in the projection-typeimage display apparatus according to the embodiment 3.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments according to the present invention will befully explained by referring to the attached drawings.

First of all, FIG. 1 attached herewith shows the entire structures of aprojection-type image display apparatus according to an embodiment 1, inparticular, applying transparent-type liquid crystal image displayelements (or panels) therein, as those for modulating light strength orintensity of three color lights, i.e., R, G and B lights, within anoptic unit.

In the figure, a light source 10 is made up with a white color lamp,i.e., so-called a high-pressure lamp, such as, the metal halide lamp orthe high-pressure mercury lamp or the like, as was mentioned above, forexample, or alternately a xenon lamp, a mercury-xenon lamp, or a halogenlamp, etc. Further, a reference numeral 11 in the figure depicts aconcave mirror (i.e., a reflector) having a reflection surface of anellipsoidal surface or a parabolic surface, which is attached aroundthat lamp, and it emits the light (i.e., white light) irradiated fromthe lamp into one (1) direction.

Next, the light emitting from this light source 10, penetrating througha pair of multi-lenses 21 and 22 disposed on an optical axis thereof(however, each multi-lens is made up with a large number lens cells,which are aligned in matrix-like), comes to be a white light having auniform light strength within an irradiation surface area, and furtherit is incident upon a polarized-light conversion element 23, which isconstructed with lines of rhombic or diamond-shaped prisms, each havingabout a half (½) size of the lens width, which are disposes to befitting to a pitch of the vertical direction on the each optical axis ofthe lenses. Upon the polarized-light conversion element 23, a polarizedlight separation film is provided on a prism surface thereof, andtherefore the incident light thereon is divided or separated into aP-polarized light and a S-polarized light through that polarized lightseparation film. The P-polarized light penetrates through the polarizedlight separation film as it is, to be emitted outside. On the otherhand, after being reflected upon the polarized light separation film andfurther being reflected again into the direction of the inherent opticalaxis within the diamond-shaped prisms neighboring to each other, theS-polarized light is rotated in the polarization direction by 90°through a λ/2 phase difference plate, which is provided on an emissionsurface of the prism. Thus, it is converted into the P-polarized lightand is emitted from. In this manner, only the P-polarized light isemitted from the polarized-light conversion element 23.

The P-polarized light from the polarized-light conversion element 23 isfurther condensed by a collimator lens 24, which has a positiverefractive power and equipped with a condensing function, and isincident upon an optic system, which will be explained below, through afilter 25, for example.

Thus, the P-polarized light incident thereupon, after being separatedG-color light therefrom through a R- and B-lights penetrating andG-light reflecting dichroic mirror 31, i.e., the G-light separatedtherefrom is further reflected upon a first white color reflectionmirror 32, to be incident upon an image display element portion whichwill be explained in details thereof later, through a collimator lens33. On the other hand, the R-light and the B-light penetrating throughthe dichroic mirror 31 mentioned above, next after being color-separatedthe B-light by a R-light penetrating and B-light reflecting dichroicmirror 34, i.e., the B-light separated therefrom is incident upon theimage display element portion through a collimator lens 33. Lastly, theR-light penetrating through a dichroic mirror 34, after penetratingthrough the collimator lens 33, is reflected upon a white lightreflection mirror 35, and further after penetrating through anothercollimator lens and reflected upon a third white light reflection mirror36, it is incident upon the image display element portion through acollimator lens 33. In this manner, the P-polarized light from the lightsource mentioned above is separated into the R-light, the B-light andthe G-light, respectively, with using the polarization thereof, and theyreach to the image display element portion which will be mentioned indetails thereof below.

However, the image display element portion 40 mentioned above comprisesan optical synthesizing means being cubic-like in the externalconfiguration thereof, which is made up with four (4) pieces oftriangular prisms, i.e., so-called cross dichroic prisms 41. And, uponthe incident surfaces of the cross dichroic prisms 41, each separatingfrom one another (but, only one (1) surface 41-1 is shown in thefigure), as is shown in FIG. 2 attached herewith, are attached a R-lightpenetration type image display element 42R, a G-light penetration typeimage display element 42G, and a B-light penetration type image displayelement 42B, respectively, in one body (or, as a unit), through jigs 43for fixing, each providing an opening 44 at a central portion of a metalplate and also projections 45 formed through cutting at every cornersthereof. Further, those of the R-light penetration type image displayelement 42R, the G-light penetration type image display element 42G, andthe B-light penetration type image display element 42B are fixed on thefixing jigs 43, respectively, through a solder or an adhesive, forexample, and they are positioned and fixed at the predetermined portionswith respect to three (3) incident surfaces, at high accuracy thereof,so as to synthesize the lights from the light source, penetratingtherethrough while being modulated the intensity thereof, respectively.

Further, as is shown in FIG. 3 attached herewith, on lower surfaces ofcross dichroic prisms 41, being attached with the R-light penetrationtype image display element 42R, the G-light penetration type imagedisplay element 42G, and the B-light penetration type image displayelement 42B thereon, there is also attached a seat portion 46, having ashape being almost similar to the cross-section of the prisms 41mentioned above, in one (1) body through ah adhesive, for example.Further, on two (2) sides of this almost square-shaped seat portion 46,neighboring to each other, are formed projection portions (or frames) 47and 47 for use of positioning, crossing on each other. With this, it ispossible to fix the seat portion 46 at the desired position on the lowersurfaces of the cross dichroic prisms 41, correctly, but only bymounting the lower surfaces of the prisms 41 on the seat portion 46 andabutting it onto the projection frames 47 and 47, simply. Further, onthe lower side surface of this seat portion are formed a plural numberof projections 48 for use of positioning (two (2) pieces in thisexample), in advance, correctly and at high accuracy, at a predeterminedposition, as will be explained later, so that it can be positioned andfixed, easily, onto the attachment structures formed on the side of theprojection lens 60.

Again, turning back to FIG. 1 mentioned above, after being modulated inthe intensity thereof through the respective penetration-type imagedisplay elements, within the image display element portion 40 which wasexplained in the above, the lights synthesized within the cross dichroicprisms 41, as being the color synthesizing means, is enlarged andprojected onto a screen 80, for example, through a projection lens, thedetails of which will be explained below. However, this image displayelement portion 40 has such the structures of being detachable opposingto the incident surface of the projection lens 60. Further, referencenumerals 61 and 62 in the figure depict a reflection-type polarizingplate and an absorption-type polarizing plate, which are provided on theincident side surface of the projection lens 60.

Following to the above, by referring to FIGS. 4 to 8 attached herewith,there is shown an example of the structures (i.e., a supporting portion)for enabling the image display element portion 40 to be detachable onthe incident side surface of the projection lens 60. As apparent fromthose figures, on the incident side surface of the projection lens 60 isprovided so-called an attachment portion 70 for the image displayelement, for attaching the image display element portion 40 thereon, ina detachable manner. However, as is also apparent from FIG. 4, thisimage display element attachment portion 70 is formed into apredetermined shape, such as, through the injection molding of plasticor the like, for example. With the present example, it is almost squarein the external configuration thereof, and further it is formed intosuch a shape that it has a projection portion 71 at around a centralportion thereof, i.e., on a surface opposing to the incident surface ofthe projection lens 60.

And, on this projection portion 71 is formed a square shaped portion 72,being opened therein, with fitting to an exit surface of the crossdichroic prisms 41 mentioned above (i.e., the surface of the crossdichroic prisms 41, but differing from those mounding the R-lightpenetration type image display element 42R, the G-light penetration typeimage display element 42G, and the B-light penetration type imagedisplay element 42B thereon). And, further below that opening portion 72is formed so-called a tongue-like fixing portion 73 in one body (or as aunit), for attaching the image display element portion 40, i.e., thecross dichroic prisms on an upper surface thereof, detachably. And, onthe upper surface of this tongue-like portion 73 are formed holes 74 and74, into which the projections 48 for use of positioning shown in FIG. 3mentioned above are inserted to be fitted, at predetermined positionsthereof, correctly and with high accuracy.

In FIGS. 5 an 6 attached herewith is shown the condition where the imagedisplay element portion 40, the detailed structures of which areexplained in the above, is mounted on the attachment portion 70 for theimage display element, which is attached on the incident side surface ofthe projection lens 60. Also, in FIG. 7 attached herewith is shown thecondition after mounting the image display element portion 40 on theattachment portion 70 for the image display element, and further, inFIG. 8 attached herewith the condition after mounting the image displayelement portion on the incident side surface of the projection lens 60,respectively.

As was mentioned above, in the projection-type image display apparatusaccording to the embodiment 1, in particular, applying thepenetration-type liquid crystal image display elements (panels) as thosefor modulating the light intensities of the three (3) color lights, R, Gand B lights, with adopting the structures for enabling to amount theimage display element portion 40, which is built up with attaching theR-light penetration type image display element 42R, the G-lightpenetration type image display element 42G, and the B-light penetrationtype image display element 42B upon the three (3) surfaces of the crossdichroic prisms, neighboring to one another, onto the image displayelement attachment portion 70 attached on the incident side surface ofthe projection lens 60, in particular, with applying the tongue-likefixing portion 73, and further the positioning projections 48 and thefitting holes 74 thereof, easily, at the correct position, in detachablemanner, it is possible to exchange only the image display elementportion 40, easily.

Thus, with the projection-type image display apparatus according to theembodiment 1, though the heat generation also comes up to be large moreand more on the liquid crystal panels, due to irradiation of thestronger light irradiated from the light radiation source upon a smallarea of the liquid crystal panel, accompanying with the remarkableimprovement for achieving the high definition and the high brightness,however according to the present invention, being accomplished by takingthe fact into the consideration thereof, that it is difficult at all tosuppress the heat generation mentioned above on the liquid crystal panelonly by the introduction and the circulation of the cooling air into theinside of the apparatus by means of the conventional air-cooling fan,while also on the other hand being achieved by paying attention onto theliquid crystal image display elements (the panels), on which improvementis made remarkably for achieving the low-costs and the small-sizingthereof in recent years, it is to bring the optic unit being inescapableor unavoidable from deterioration thereof due to the heat generationmentioned above, in particular, the image display element portion madeup with the cross dichroic prisms equipped with the liquid crystal imagedisplay elements (i.e., the panels), to be exchangeable with a new imagedisplay element portion, with easy or simple work, depending onnecessity thereof, accompanying with the deterioration thereof, andthereby enabling to obtain the desired optical performance, alwaystherefrom.

Also, within the projection-type image display apparatus according tothe embodiment 1, it is preferable to provide a supporting portion formounting the cross dichroic prisms thereon, on which the displayelements are attached, in a freely detachable manner, in particular, onthe incident surface side of the projection lens, or to fix a member forpositioning on a surface of the cross dichroic prisms where no displayelement is attached, to be attached onto that supporting portion, whichis provided on the incident surface side of the projection lens. And, itis also preferable to put a member for preventing the reflection betweenthe incident surface side of the projection lens and the projectionlens.

In more details thereof, as is apparent from the above-mentioned, in themanufacturing processes thereof, it is possible to fix the image displayelement portion 40 at the correct position on that seat portion 46,which is built up with the R-light penetration type image displayelement 42R, the G-light penetration type image display element 42G, andthe B-light penetration type image display element 42B, being attachedat high accuracy on the three (3) pieces of surfaces of the crossdichroic prisms 41, neighboring to one another, but only through fixingit while abutting onto the positioning projection frames 47 and 47 onthat seat portion 46. Then, with a simple work, i.e., inserting thepositioning projections 48 formed on the lower surface of that seatportion 46 into the fitting holes 74, which are formed on a surface ofthe tongue-like fixing portion 73 of the image display elementattachment portion 70, it is possible to position that image displayelement portion 40, again, correctly, with respect to the optic systemof the projection-type image display apparatus mentioned above, inparticular, on the light paths of R-light, G-light and B-light thereof.

Also, the reflection-type polarizing plate 61 and the absorption-typepolarizing plate 62 are disposed on the incident surface side of theprojection lens 60 (i.e., between the projection lens 60 and the crossdichroic prisms 41), according to the embodiment 1 mentioned above, andthereby building up the structures for absorbing the reflection ofincident light upon the projection lens 60. With such the structures, itis possible to obtain the projection-type image display apparatusprohibiting to generate a ghost or the like due to the reflection light,for example, i.e., being more superior in the optical performancesthereof. Further in more details thereof, it is preferable to set adegree of polarization of the main reflection-type polarizing plate 61to be larger than that of the absorption-type polarizing plate 62, sinceit is possible to absorb the reflection light upon the projection lensmuch more therewith. However, those reflection-type polarizing plate 61and absorption-type polarizing plate 62 are separated from the imagedisplay element portion 40, i.e., they are not detachable in thestructures thereof.

FIG. 9 attached herewith shows the projection-type image displayapparatus, according to an embodiment 2. As is apparent from the figure,in particular, according to this embodiment 2, it is so constructed thatthe optical paths within the inside thereof can be protected from dusts,which are introduced from an outside of the apparatus, by disposing theoptic system, i.e., for separating the lights emitting from the lightsource 10 into the colors thereof, and thereby entering them upon thethree (3) pieces of surfaces of the cross dichroic prisms 41 building upthe image display element portion 40 neighboring to one another, i.e.,the R-light penetration type image display element 42R, the G-lightpenetration type image display element 42G, and the B-light penetrationtype image display element 42B, within an inside of a dustproof housing90 made of a plastic, for example.

In more details thereof, as is apparent from the figure, the pair of themulti-lenses 21 and 22, the polarized-light conversion element 23, thecollimator lens 24 and the filter 25, further the R- and B-lightspenetrating and G-light reflecting dichroic mirror 31, the first whitecolor reflection mirror 32 and the collimator lens 33, further theR-light penetrating and B-light reflecting dichroic mirror 34 and thecollimator 33, and further the second white light reflection mirror 35,the collimator lens 33, the third white light reflection mirror 36, andthe collimator lens 33 are sealed within the housing 90 made of aplastic, air-tightly.

With the embodiment 2, the details of which was explained in the above,there was mentioned only the case of applying the penetration-typeliquid crystal image display elements (i.e., the panels), in particular,to be the liquid crystal image display elements (i.e., the panels) formodulating the light intensities of the three (3) color lights, i.e.,the R-light, G-light and B-light, within the optic unit thereof;however, it would be apparent that the present invention should not berestricted only to such the penetration-type liquid crystal imagedisplay elements (i.e., the panels), but is also applicable into theprojection-type image display apparatus adopting the refection-typeliquid crystal image display elements (i.e., the panels), for example,in the place thereof.

FIGS. 10 and 11 attached herewith show the structures, mainly around areflection polarized-light prism, including cross dichroic prisms 410and the liquid crystal image display elements (i.e., the panels)attached on the three (3) neighboring surfaces thereof, in particular,being constructed to be detachable onto the apparatus, in case ofapplying reflection type liquid crystal image display elements (i.e.,panels), according to an embodiment 3.

First, FIG. 10 shows the structures of the projection-type image displayapparatus applying such reflection-type liquid crystal image displayelements (i.e., the panels) as was mentioned therein, wherein theP-polarized light emitted from the light source similar to thatmentioned above, after being separated in the color into thereof G-lightupon a R- and B-lights penetrating and G-light reflecting dichroicmirror 31′, and in particular, the G-light separated, it is reflectedupon a first white color reflection mirror 32′ through a collimator lens33′, and after being incident upon a correction polarization plate 37through that collimator 33′, again, is incident upon an image displayelement portion 400 having a reflection-type polarization prism therein.On the other hand, R-light and B-light penetrating through the dichroicmirror 31′ are separated in the color thereof, next, upon a R-lightpenetrating and B-light reflecting dichroic mirror 34′, and thereafterthe B-light separated is incident upon the image display element portion400. Finally, the R-light penetrating through the dichroic mirror 34′ isalso incident upon the image display element portion 400, in the similarmanner.

However, as is apparent from the figure, this image display elementportion 400 comprises cross dichroic prisms 410, i.e., a lightsynthesizing means being cube-like in the outer configuration thereof,and combining four (4) pieces of triangular prisms with, and onto thethree (3) pieces of surfaces thereof, neighboring to one another, areconnected or bonded a R-light reflection-type image display prism 420R,a G-light reflection-type image display prism 420G, and a B-lightreflection-type image display prism 420B, respectively, so as to buildup necessary light paths. And, upon surfaces of those reflection-typeimage display prisms 420 opposing to the bonding surfaces thereof areattached a reflection-type G-light liquid crystal image display element(i.e., panel) 450G, a reflection-type B-light liquid crystal imagedisplay element (i.e., panel) 450B, and a reflection-type R-light liquidcrystal image display element (i.e., panel) 450R, respectively, throughan analyzer 430 and a ½ wavelength plate 440 each. Further, a referencenumeral 460 in the figure depicts convex lenses, which are attached onside surfaces of the reflection-type image display prisms 420, for thepurpose of introducing the R-, G- and B-lights therein, respectively.Also, it is possible to build up the optical paths necessary, by usingreflection-type of polarized-light mirrors, not shown in the figure, butin the place of the reflection-type image display prisms 420.

Within the projection-type image display apparatus applying thereflection-type liquid crystal image display elements (i.e., the panels)having such the structures therein, but similar to those shown in theembodiments 1 and 2, the optic image is formed through the crossdichroic prisms 410, functioning as being the color synthesizing meansafter modulating the light intensities of the lights through the R-, G-and B-lights reflection-type image display prisms 420 mentioned above,and it is projected onto the screen 80 or the like, through theprojection lens 60.

Next, FIG. 11 shows the image display element portion 400, the detailedstructures of which was explained in the above, and in particular, thestructures for attaching or mounting the cross dichroic prisms 410,including the reflection-type image display prisms 420. However, in thisembodiment, also in the similar manner to that shown in FIG. 3 mentionedabove, a bottom surface of the cross dichroic prisms 410 is fixed ontoan upper surface of the seat portion 46 mentioned above, with using thepositioning projection frames 47 and 47 formed thereupon. And, thepositioning projections 48 formed on the lower surface of that seatportion 46 into the fitting holes 74, which are formed in advance on thesurface of the tongue-like fixing portion 73 of the image displayelement attachment portion 70, are also inserted into the fitting holes74 and 74, which are formed on the surface of the tongue-like fixingportion 73 of the image display element attachment portion 70, thedetails of which were explained in FIG. 4 mentioned above, and therebyenabling this image display element portion 400 to be attached ormounted at the correct position, simply or easily, in a detachablemanner.

As was mentioned above, also with the projection-type image displayapparatus applying therein the liquid crystal image display elements(i.e., panels) 450 explained in the above, in the similar manner, theoptic unit, inescapable from the deterioration thereof accompanying withthe remarkable advances in the high definition and the high brightnessin recent years, can be built up with the reflection-type image displayelements (i.e., the panels), depending on the necessity thereof, i.e.,the cross dichroic prisms 410, including the reflection-typepolarization prisms 420, etc., can be formed in one body (as a unit), tobe exchangeable with a new image display element portion through simpleworks, thereby enabling it to exhibit or keep the desired opticalperformances thereof, always.

In more details, as is similar to that mentioned above, in themanufacturing processes thereof, it is also possible to position theimage display element portion 400, again, correctly on the light pathsof R-light, G-light and B-light, only by fixing the image displayelement portion 400 at the correct position on that seat portion 46,which is built up with the cross dichroic prisms 410 and also the R-, G-and B-light reflection-type polarization prisms 420 attached on thethree (3) surfaces thereof neighboring to one another, and alsoinserting this into the fixing holes 74 which are disposed and formedcorrectly on the surface of the tongue-like fixing portion 73 of theimage display element attachment portion 70.

In addition thereto, according to the embodiment 3, it is also possibleto achieve the projection-type image display apparatus being moresuperior in the optical performances thereof, i.e., prohibiting togenerate a ghost or the like due to the reflection light, for example,with disposing the reflection-type polarizing plate 61 and theabsorption-type polarizing plate 62 on the incident surface side of theprojection lens 60 (i.e., between the projection lens 60 and the crossdichroic prisms 410). Also, in the similar manner to that of FIG. 9mentioned above, it is also possible to obtain the structures forprotecting the optical paths within the inside thereof, while disposingthe optic system, which guides the lights incident upon the three (3)pieces of surfaces of the image display element portion 400 neighboringto one another, within the housing 90 made of a plastic, for example.

In the projection-type image display apparatus according to theembodiment 3, it is preferable to provide the supporting portion on theincident surface side of the projection lens, for attaching or mountingthe cross dichroic prisms thereon in detachable manner, each of which isattached with the display element. And, it is also preferable to fix themember for positioning on the surface of the cross dichroic prisms whereno display element is attached, to be attached onto the supportingportion, which is provided on the incident surface side of theprojection lens. Further, for each of the cross dichroic prisms, it ispreferable to comprise the reflection-type polarizing prism, which isfixed on the surfaces neighboring to each other, and it is alsopreferable that the R-, G- and B-light reflection-type image displayelements are attached on different surfaces of the reflection-typepolarizing prisms. In addition thereto, it is also preferable to put amember for antireflection between the exit side of the cross dichroicprisms and the projection lens.

In those embodiments 1 to 3, although the explanation was given on anassumption that the P-polarized lights can be obtained from theillumination system (i.e., the light source 10 mentioned above); howeverthey should not be restricted only to that. For example, it may be soconstructed that only S-polarized lights can be emitted from, in theplace thereof. However, in more details thereof, in case where thelights emitted from the light source 10 building up the illuminationsystem are the S-polarized lights, those lights are reflected upon thereflection-type polarization prisms 420, functioning as being thepolarized-light conversion devices, and they are converted into theP-polarized lights in conformity with image signals through thereflection-type liquid crystal image display elements (i.e., panels)450G, 450B and 450R, to be incident upon the cross dichroic prisms(i.e., the color synthesizing device) 410. In this instance, by takingthe characteristics of the prisms mentioned above into the considerationthereof, in particular, with provision of a λ/2 plate between thepolarized-light conversion devices (i.e., the reflection-typepolarization prisms 420B and 420 R) thereof, corresponding to B-lightand R-light, and the cross dichroic prisms 410 building up the colorsynthesizing device, it is possible to change the incident lights uponthat prisms into the S-polarized lights, and thereby obtainingpreferable dichroic characteristics.

As is apparent from the above, with the projection-type image displayapparatuses, according to the embodiments 1 to 3, enabling the crossdichroic prisms, each being attached with the display element thereon,to be mounted detachably, it is possible to exhibit or keep the desiredoptical performances thereof, always, by exchanging the prisms with anew image display element portion, depending upon the necessity,accompanying with deterioration of the performances thereof, with simpleworks.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential feature or characteristicsthereof. The present embodiment(s) is/are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than by theforgoing description and range of equivalency of the claims aretherefore to be embraces therein.

1. A projection-type image display apparatus, comprising the followingin a housing thereof: a light source; a lighting optical system;penetration-type image display elements configured for use of R-color,G-color and B-color; an optical synthesizing portion; and a projectionlens, wherein: said projection-type image display elements configuredfor use of the R-color, G-color and B-color are attached with a crossdichroic prism, which constructs said optical synthesizing portion, inone body, on optical surfaces thereof differing from each other, saidcross dichroic prism attached with said image display elements can befreely and detachably attached, so that an emission surface differingfrom the surfaces, on which said image display elements are attached,opposes to an incident surface of said projection lens, and also areflection-type polarizing plate and an absorption-type polarizing plateare disposed, sequentially, between the emission surface of said crossdichroic prism and the incident surface of said projection lens, fromthe emission surface of said cross dichroic prism, opposing to saidcross dichroic prisms, and the degree of polarization of saidreflection=type polarizing plate is larger than that of saidabsorption-type polarizing plate.
 2. The projection-type image displayapparatus, according to claim 1, wherein on a side of the incidentsurface of said projection lens is provided a support member forattaching said cross dichroic prism, on which said image displayelements are attached, freely and detachably.
 3. The projection-typeimage display apparatus, according to claim 2, wherein a memberconfigured for use of positioning is attached on said support member, onthe side of the incident surface of said projection lens, by fixing saidmember configured for use of positioning on one surface, on which saidcross dichroic prism is not attached and further said reflection-typepolarizing plate and said absorption-type polarizing plate are notdisposed.
 4. A projection-type image display apparatus, comprising thefollowing is a housing thereof: a light source; a lighting opticalsystem; penetration-type image display elements configured for use ofR-color, G-color and B-color; an optical synthesizing portion; and aprojection lens, wherein: said penetration-type image display elementsconfigured for use of the R-color, G-color and B-color are, at least,attached with a cross dichroic prism, which constructs said opticalsynthesizing portion, in one body together with said cross dichroicprism, on optical paths opposing surfaces of said cross dichroic prismdiffering from each other, said cross dichroic prism attached with saidimage display elements can be freely and detachably attached, so that anemission surface differing from the surfaces, on which said imagedisplay elements are attached, opposes to an incident surface of saidprojection lens, and also a reflection-type polarizing plate and anabsorption-type polarizing plate are disposed, sequentially, between theemission surface of said cross dichroic prism and the incident surfaceof said projection lens, from the emission surface of said crossdichroic prism, opposing to said cross dichroic prisms, and the degreeof polarization of said reflection-type polarizing plate is larger thanthat of said absorption-type polarizing plate.
 5. The projection-typeimage display apparatus, according to claim 4, wherein on a side of theincident surface of said projection lens is provided a support memberfor attaching said cross dichroic prism, on which said image displayelements are attached, freely and detachably.
 6. The projection-typeimage display apparatus, according to claim 5, wherein a member for useof positioning is attached on said support member, on the side of theincident surface of said projection lens, by fixing said member for useof positioning on one surface, on which said cross dichroic prism is notattached and further said reflection-type polarizing plate and saidabsorption-type polarizing plate are not disposed.
 7. Theprojection-type image display apparatus, according to claim 5, whereinsaid cross dichroic prism has reflection-type polarizing prisms, whichare fixed on surfaces neighboring with each other, and said R-color,G-color and B-color display elements are attached on saidreflection-type polarizing prisms, on surfaces differing thereof fromeach other.